1. Field of the Invention
The present invention relates to a technique for measuring the temperature of an object such as a substrate used in the fields of the manufacture of semiconductors and liquid-crystal devices. Specifically, the present invention relates to a temperature-measuring member configured to measure the maximum temperature of the object in a temperature profile, a temperature-measuring device, and a method for measuring a temperature.
2. Description of the Related Art
Typical examples of a temperature-measuring member configured to measure the temperature of a target object include a member utilizing a change in the thermal expansion coefficient of a gas or liquid; a member measuring a change in the electrical resistance of a metal with temperature (platinum resistance thermometer); a member measuring a change in semiconducting property with temperature (thermistor); a member measuring a thermoelectromotive force generated at the contact point of different alloys (thermocouple); a member measuring the intensity of infrared radiation from a target object (infrared thermometer); and a member measuring the magnetized state of a target object after a magnetic field is applied to the target object (for example, see Japanese Unexamined Patent Application Publication Nos. 9-5166 and 9-113379). Furthermore, label-type temperature-measuring members utilizing melting points of substances are commercially available.
Temperature measurement is performed in various circumstances. Temperature-measuring members are appropriately selected in accordance with target objects. In particular, thermocouples are used as precise temperature-measuring members in many fields.
Also in the fields of the manufacture of semiconductors and liquid-crystal devices, temperature measurement is performed everywhere. In the field of the manufacture of liquid-crystal devices, substrates are mainly composed of glass. Thus, heat treatment is often performed at a temperature equal to or lower than the allowable temperature limit of glass, i.e., about 150° C. to about 400° C. In the field of the manufacture of semiconductors, heat treatment is often performed in the range of about 150° C. to about 600° C., which is slightly higher than the temperature range above.
On production lines in the fields of the manufacture, in general, substrates are conveyed while being subjected to temperature profiles in heat-treatment furnaces and heated deposition systems. Thus, it is difficult to directly measure the temperature of substrates with, for example, thermocouples. The temperature of substrates is usually estimated by measuring the temperature of atmospheres in furnaces and systems.
If the temperature of substrates can be directly measured with precision, the accuracy of process control is improved. This contributes to achieving higher performance of products. Such situations are commonly recognized in many fields of manufacture as well as the fields of the manufacture of semiconductors and liquid-crystal devices.
For example, when a target object is transported (in other words, continuously moved), a temperature-measuring member that needs to be connected to leads, e.g., a thermocouple, cannot be used. In such a case, an example of temperature-measuring members capable of measuring the temperature of the target object is a noncontact thermometer such as a radiation thermometer.
In the case where the noncontact thermometer is used, however, to measure the temperature of the target object subjected to a temperature profile, it is necessary to move the noncontact thermometer with the transportation of the target object or to install many noncontact thermometers along the transport direction of the target object, thereby disadvantageously complicating facilities and increasing equipment cost. Furthermore, when the target object is totally enclosed, an observation cannot be made on the target object. Thus, the noncontact thermometer cannot be used.
Another example of a temperature-measuring member that does not need to be connected to leads is a label-type temperature-measuring member. Such a label-type temperature-measuring member includes a plurality of pigments that change color and that are provided between resin sheets in 10° C. or 25° C. steps. The label-type temperature-measuring member has the advantage of simplicity and excellent accuracy. However, the label-type temperature-measuring member contains the resin component; hence, it is difficult to measure a temperature of 250° C. or higher. Furthermore, the label-type temperature-measuring member utilizes the melting phenomenon of the materials, thereby possibly generating impurities due to the evaporation of the molten materials. Thus, when the substrate must not be contaminated with the impurities, the label-type temperature-measuring member cannot be used.
In recent years, a wafer sensor in which temperature sensors, an IC recorder, and a battery are incorporated in the wafer has been developed. A temperature profile to which a target substrate is subjected can be measured with the wafer sensor. However, since the battery and semiconductor elements are used, the temperature range that can be measured with the wafer is at most about 150° C. It is thus difficult to measure a temperature higher than about 150° C.
Examples of a temperature-measuring member that can measure the maximum temperature without electrical wiring include a member utilizing a change in the volume of a ceramic material during sintering; and a member utilizing the softening of a ceramic material (Seger cone). However, these temperature-measuring members composed of ceramic materials are used in a high temperature range, i.e., 800° C. to 1,000° C. or higher. Thus, these temperature-measuring members are not suitable for temperature measurement in the range of about 150° C. to about 600° C., the temperature range being required for the fields of the manufacture of semiconductors and liquid-crystal devices.